This invention relates to a method of producing reinforcing members to be used in tires and having elongations which do not detrimentally affect tire performance and enable stresses to be uniformly distributed in width directions without any stress concentration.
Rubber members having cords embedded therein have been widely used as elastic members having a cut-resistant property in various fields. When such elastic members are used in structures subjected to various external forces such as tires, in addition to the cut-resistant property they are required to have elongations to an extent such that they do not affect tire performance.
From this viewpoint, there have been elastic members realizing suitable elongations with the aid of wave-shaped cords embedded therein. Various kinds of methods of producing such elastic members have been proposed.
A few of the methods will be explained herein referring to FIGS. 1-3.
A first example is a spiral stripe method disclosed in Japanese Patent Application Laid-open No. 47-13,684. As shown in FIG. 1, stripes 01 are embraced between rubber-like elastic members 02 and 03 and embedded therein. On the way of supplying the stripes, they are caused to pass through a fixed pattern plate 05 and working pattern plates 04 moved along orbits of circular arcs, so that the stripes 01 are permanently spirally set or deformed. After the deformed stripes 01 have passed through a guide unit 06, they are pressed between rubber-like elastic members 02 and 03 by means of upper and lower pressure guide rollers 07 and 08 to form a rubber-like reinforced elastic structure having wave-shaped stripes embedded therein.
As second example shown in FIG. 2 is a gear setting method disclosed in Japanese Patent Application Laid-open No. 52-91,967. One fiber web 012 is transferred in its longitudinal direction by a chain conveyor 017. A plurality of fiber yarns 011 are supplied onto an upper surface of the chain conveyor 017 with substantially equal intervals in its width directions.
In order to supply the fiber yarns, a pair of gear-shaped rollers 014 and 015 are used, which have on their outer circumferences a plurality of crests and valleys. Fiber stripes 011 are supplied from a creel 010 and passed through the rollers 014 and 015 immediately before they arrive onto the upper surface of the web 012 so that the stripes 011 are shaped into wave-forms with substantially equal pitches in their lengthwise.
At a location where the fiber web 012 supporting the plurality of the wave-shaped fiber stripes 011 has been somewhat transferred in the longitudinal direction, another fiber web 013 is supplied onto the fiber stripes 011. The assembled stripes and webs are then subjected to needle-punching by means of needling means 016 to obtain an unwoven cloth 018.
A third example shown in FIG. 3 is a zigzag belt method disclosed in Japanese Patent Application Laid-open No. 61-502,877. A flexible endless belt 022 extends about cylindrical members 020 and 021. Coated continuous cord reinforcing stripes 023 in the form of waves are shaped in wave-forms on the endless belt 022.
In more detail, the continuous cord reinforcing stripes 023 are supplied through suitably shaped grooves in matching means 024 and between rollers 025 and 026 rotating in opposite directions and forcing the stripes 023 against the endless belt 022.
The matching means 024 is connected through control belts 028 to a support 027 reciprocatively driven by means of a cylindrical cam device 026.
The cord reinforcing stripes 023 are thus supplied onto the endless belt 022 in zigzag patterns over the width of the endless belt 022.
Among the above three examples, in the spiral stripe method and the gear setting method of the first and second examples, stripes susceptible to plastic deformation such as steel cords are easy to be permanently set into wave-forms. However, these methods could not be used for soft cords such as chemical fibers because they are difficult to be permanently set.
Moreover, it is difficult to make uniform pitches and intervals of the waves of cords. Unevenness in wave in width directions and overlaps of cords often occur which would cause stress concentration and in many cases detrimentally affect life of tires and become one source of troubles in tire.
Further, modification in wave-form could not be easily carried out so that these methods could not meet various needs in the field.
In case of cords being overlapped, thicknesses of formed reinforcing members become uneven so that tire performance is detrimentally affected. Moreover, air is accumulated in the overlapped portions of cords. In worst cases, the accumulated air may cause separation of reinforcing members.
In the zigzag belt method of the third example, the coated cord reinforcing stripes are used so that an apparatus for coating the cords is needed. In the method, such coated cords are arranged one upon the other so that the air is likely to be accumulated between the cords.
In the zigzag belt method, moreover, the number of the coated cords arranged on the endless belt during one operation cycle is so limited that production efficiency remains at low value.